Entry 1 sense Webster, 1913 Sulphionide · Sulph·i·on·ide · IPA 01 n. A binary compound of sulphion, or one so regarded; thus, sulphuric acid, H2SO4, is a sulphionide. 1. A binary compound of sulphion, or one so regarded; thus, sulphuric acid, H2SO4, is a sulphionide.(Chem.)